I'm clued up on engines but not diesel fuel systems.
one of the first things ever you should check on any vehicle with fuel problems is the fuel cap breather, now i know that there is some sort valve in it ..make sure this isn't the culprit by running with the fuel cap removed.
next pick out all the things that don't cost major money to replace, check , clean or replace.
starting with fuel filter and bleeding
https://www.youtube.com/watch?v=_X7q77ENVbUalso pump some diesel out, let it settle for half an hour and look for water in a clear glass
that's as far as i can help.
all the best..mark